These subjects are generally known.
DE 39 25 104 A1 discloses an apparatus for the regulation of strip thicknesses in single-stand cold-rolling mills, in which the apparatus has an uncoiler for the strip part running into the rolling stand in the cold-rolling mill and a coiler for the strip part running out of the rolling stand. A device for regulating the speed at which the uncoiler rotates is provided in the sense that the speed of the strip part running in is regulated in relation to the speed of the strip part running out according to the setpoint pass reduction. DE 39 25 104 A1 also states that the corresponding mass flow principle is realized by these measures, and that the use of this principle for regulating multi-stand cold-rolling mill trains is known in principle.
In the case of multi-stand cold-rolling mill trains, the strip thicknesses and the strip tensions are normally set on the basis of the mass flow regulation concept, preferably in the extended variant, according to which a strip feeding device arranged on the inlet side is regarded as a initial rolling stand. The setpoint strip thicknesses are set virtually automatically by virtue of the guideline relating to the strip speeds in the individual sections of the multi-stand rolling mill train (i.e. between two respective directly adjacent rolling stands). However, since the actual speeds of the cold strip in the individual sections can be set only indirectly by way of the circumferential speeds of the rolls in the rolling stands, the lead of the actual speeds of the cold strip in the individual sections in relation to the roll speeds is a factor of uncertainty. The increasingly stringent demands made on the dimensional stability of the rolled products therefore require new methods in order to be able to eliminate these uncertainties in relation to the lead.
In order to solve the problem mentioned above, it is known to damp thickness defects resulting from the unknown leads in the intermediate stands by means of a thickness control loop in the outlet of the cold-rolling mill train. Particularly in the most common mode of operation, in which the last rolling stand in the cold-rolling mill train operates in skin-pass mode (i.e. only with a very small reduction in thickness of, for example, 1% to 2%), the slow monitor regulation at the outlet of the cold-rolling mill train is only able to correct these thickness defects inadequately.
It is known to model the lead on the essential working points of each rolling stand. The circumferential speeds of the rolls are thereby subject to pilot control, in such a way that the actual speeds of the cold strip in the individual sections are as close as possible to the corresponding setpoint values.
Furthermore, if—as is possible in particular in the case of cold-rolling mills having a tension bridle in the inlet—the material flow running in can be fixed at a setpoint mass flow, the uncertainties in relation to lead scarcely have an effect on the target thickness quality when employing the known tension regulation concepts.